QMI IPv6 crashes

[Bjørn Mork]

Dan Williams <dcbw at redhat.com> writes:
> On Thu, 2014-04-24 at 20:48 +0200, Bjørn Mork wrote:
>> Dan Williams <dcbw at redhat.com> writes:
>> 
>> > Hi,
>> >
>> > I did some testing with the UML290 on both Verizon (LTE) and T-Mobile
>> > (UMTS) and got odd results from GetCurrentSettings, and couldn't get any
>> > connectivity:
>> >
>> > [mm-bearer-qmi.c:382] get_ipv6_config(): QMI IPv6 Settings:
>> > [mm-bearer-qmi.c:393] get_ipv6_config():     Address: 2600:1014:b005:6ff1:7824:b541:88db:58c8/64
>> > [mm-bearer-qmi.c:399] get_ipv6_config():     Gateway: d42f:cc9d:967a:4442::
>> > [mm-bearer-qmi.c:410] get_ipv6_config():     DNS #1: 2001:4888:3a:ff00:304:d::
>> > [mm-bearer-qmi.c:421] get_ipv6_config():     DNS #2: 2001:4888:39:ff00:308:d::
>> >
>> > This matches the raw QMI output, eg:
>> >
>> >>>>>>>   type       = "IPv6 Secondary DNS Address" (0x28)
>> >>>>>>>   length     = 16
>> >>>>>>>   value      = 20:01:48:88:00:39:FF:00:03:08:00:0D:00:00:00:00
>> >>>>>>>   translated = { [0] = '8193 ' [1] = '18568 ' [2] = '57 ' [3] =
>> > '65280 ' [4] = '776 ' [5] = '13 ' [6] = '0 ' [7] = '0 '}
>> >
>> > Now what is up with that...  neither the gateway nor the DNS servers are
>> > actually valid IPv6 addresses?  Clearly stuff didn't work.
>> 
>> Huh? The DNS server addresses look both valid and reasonable to me.
>> 2001:4888::/32 is allocated to Verizon, and there is nothing technically
>> wrong with those addresses - is there?
>> 
>> The gateway looks suspicious though.  It is in a reserved part of the
>> address space:
>> http://www.iana.org/assignments/ipv6-address-space/ipv6-address-space.xhtml
>> I guess it could work nontheless, as long as the modem responds to NS
>> for that address and the host doesn't sanity check it.  But it makes
>> more sense using some other address pointing to the modem, if you can.
>> Or try disabling ARP (i.e. ND) and just point the default route to the
>> wwan0 device.
>> 
>> Maybe using the RAs at least for the default route makes more sense?
>> That's what you'll do in almost every other case.  Or doesn't the modem
>> respond to RS? Do you see any other IPv6 packets from the modem?
>
> Update on this.  I've tested a number of different devices with two
> different SIMs where both carriers support IPv6.
>
> Novatel USB551L + Verizon: V4V6 works fine
> Novatel USB551L + T-Mobile: V4V6 crashes the modem
> Huawei E398 + Verizon: V4V6 works fine
> Huawei E398 + T-Mobile: V4V6 works fine
> Sierra MC7750 + Verizon: V4V6 works fine in Windows
> Sierra MC7750 + Verizon: V4V6 crashes modem in Linux

The last one is very interesting as it is a sign that we can avoid the
crash by doing "something" differently.  But I have no clue what that
could possibly be.  Maybe it's because we use a different MAC address?
Or maybe it's our DAD packets messing up the modem?

Does the Novatel USB551L + T-Mobile work in Windows as well?

Did you try disabling anything that might possibly send anything
unexpected to the modem (SLAAC, ND, whatever)?  In theory the connection
should still work with a statically assigned address, default routing
out the interface and no ND.


Bjørn